Web Share: Add cmp@ and dmurph@ OWNERS

Change-Id: I117057cb9ca420b082fa7e66a5362b2c41866483
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2615720
Auto-Submit: Eric Willigers <ericwilligers@chromium.org>
Reviewed-by: Chase Phillips <cmp@chromium.org>
Commit-Queue: Eric Willigers <ericwilligers@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841317}

chrome/browser/webshare/OWNERS

+cmp@chromium.org
+dmurph@chromium.org
 ericwilligers@chromium.org
 mgiuca@chromium.org